Integration, catalyzed by the viral integrase protein, is an essential step in the life cycle of all retroviruses. This has highlighted the human immunodeficiency virus type 1 (HIV- 1) integrase protein as an important target for therapeutic intervention, and the first integrase inhibitor, raltegravir, was approved for use with AIDS patients in 2007. Because raltegravir-resistance arises in patients, there is an ongoing, important need to develop next generation inhibitors that will work to counteract drug-resistant strains, and this work is underway in the pharmaceutical industry. Such drug design efforts are helped significantly by knowledge of detailed structures of the targeted protein, as well as structures of drug-bound complexes. Drugs like raltegravir preferentially bind to and inhibit the integrase-DNA complex or intasome that forms after reverse transcription as compared to the free integrase protein, highlighting the crucial need for structural information on the HIV-1 intasome. Until recently, there was no experimentally derived structure for any retroviral intasome, but work conducted during the ongoing grant platform culminated in solving the x-ray crystal structure of the prototype foamy virus (PFV) intasome. To begin to understand the analogous HIV-1 structure, we have built a molecular model using the PFV structure as a scaffold, and work proposed herein will evaluate numerous integrase-DNA contacts unveiled in the model for their roles in integration in vitro and during virus infection. We moreover will adopt what we have learned during our extensive studies with PFV and apply this knowledge to solve the three-dimensional structure of the HIV-1 intasome. The HIV-1 structure will be an invaluable asset for basic research as well as clinical scientists, as it will define the structural basis of HIV-1 DNA integration and provide a crucial platform for development of next generation integrase inhibitors. PUBLIC HEALTH RELEVANCE: Three-dimensional structures of therapeutically valuable drug targets are lynchpins of drug-design efforts. Herein we will solve the three-dimensional structure of the human immunodeficiency virus (HIV) integrase-DNA complex that is currently targeted by first- in-class integrase inhibitors. The structure will be invaluable for next generation design efforts aimed at inhibiting integrase drug-resistant strains and the spread of HIV/AIDS.